1. Field of the Invention
The invention relates to apparatus for lowering loads, and more particularly to such an apparatus which may be used to lower a load at a fixed rate or which may be controlled by a person to lower himself at a variable rate.
2. Description of the Prior Art
Numerous load lowering devices have been developed which may be used by a person to lower himself from a precipitous height. Such devices are commonly used in mountain climbing, as emergency escape devices from tall buildings, and the like. Such prior devices have generally employed a slider assembly which frictionally engages and slides downwardly along a rope. It is also known to provide some means of increasing the frictional engagement or contact with the rope so that a person using the device to lower himself can slow or stop his descent, and one such device is shown in U.S. Pat. No. 3,357,520.
The prior devices have not been entirely satisfactory for various reasons. For example, frictional contact between a conventional twisted rope and a slider member moving along the rope tends to produce a twisting or turning movement which can make it difficult for a person lowering himself to maintain his orientation relative to a wall, cliff, or the like along which he is descending. Further, many such prior devices have required a person to continuously use his hands to maintain the frictional contact between the slider and the rope in order to control the rate of descent. This has presented difficulties for persons lowering themselves along structures of formations having outwardly projecting proportions such as ledges on a building which normally require use of the hands to guide safely by.
Another defect of the prior art devices is that they generally do not provide means for increasing the rate of descent where it is safe to do so or where desirable because of a hazardous atmosphere or the like, and at the same time enabling positive control of the braking apparatus to safely slow the descent.